When a driver uses a navigation apparatus of a vehicle, the driver initially inputs a destination position to a navigation apparatus. The navigation apparatus generates a route from a current position to the inputted destination position. After starting to drive, the navigation apparatus instructs route guidance (for example, instructions such as turning right, turning left, go straight) based on the route. However, the driver may not follow the route guidance. That is, the vehicle may deviate from the route in some cases. For example, when the vehicle drives on a freeway, the driver may miss an exit guided by the navigation apparatus due to difficulty of lane change by traffic congestion. In this case, the navigation apparatus may recalculate a new route to the destination position, and generates an alternative route guides to a new exit. The navigation apparatus provides new route guidance to the driver. However, the newly suggested exit may be inappropriate for the driver in a certain condition such as too close, congested traffic, construction work. The driver may miss it again due to situations at the time of recalculation such as driving at high speed, surrounding environment.
A vehicle capable of performing an autonomous drive has an autonomous drive apparatus. In the vehicle capable of performing an autonomous drive (an autonomous drive vehicle), the driver inputs his/her destination at the start of using the autonomous drive apparatus or at a time when the driver wants to use the autonomous drive apparatus. The navigation apparatus may calculate and generate a route (referred to as an original route in the present application) and provides route guidance to the autonomous drive apparatus. When the vehicle starts an autonomous drive mode, the autonomous drive apparatus controls speed, steering operation, blinker or the like of the vehicle based on the route guidance.
As similar to the above case when the driver drives the vehicle in accordance with the route guidance of the navigation apparatus, the vehicle during the autonomous drive mode may deviate from the route guidance. That is, the vehicle during the autonomous drive mode may not leave a freeway through an exit guided by the navigation apparatus due to congested traffic, construction work, or the like. In this case, the navigation apparatus may recalculate a new route (referred to as an alternative route in the present application) based on the current position and the destination position by considering execution of the autonomous drive mode. In other words, the navigation apparatus may generate the alternative route in a premise that the vehicle remains the autonomous drive mode. However, the alternative route may be inappropriate for the driver who be in a hurry. In addition, the vehicle during the autonomous drive mode may not go along the alternative route due to a condition such as congested traffic, construction work. In that situation, the drive during the autonomous drive mode may recalculate again. When the vehicle during the autonomous drive mode keeps missing exits on a freeway, a time may be consumed much more than a case where the driver drives the vehicle.